Fuel feeding system for gas turbine engines



Jan. 22, 1963 H. J. WILLIAMS FUEL FEEDING SYSTEM FOR GAS TURBINE ENGINES Original Filed Aug. 5, 1948 4 Sheets-Sheet 1 Jan. 22, 1963 J, WILLIAMS 3,074,472

FUEL FEEDING SYSTEM FOR GAS TURBINE ENGINES Original Filed Aug. 3. 1948 4 Sheets-Sheet 2 i ma.

' INVENTOR ATTO/iwf? Jan. 22, 1963 H. J. WILLIAMS 3,074,472

FUEL FEEDING SYSTEM FOR GAS TURBINE ENGINES 4 Sheets-Sheet 3 Original Filed Aug. 3. 1948 /N VEN 70K Jan. 22, 1963 H. J. WILLIAMS FUEL FEEDING SYSTEM FOR GAS TURBINEV ENGINES 'original Filed Aug. s. 1948 4 Sheets-Sheet 4 o w E m :L 0L MM E MM5 WN 1 0m @NM L 050 FAC /rL FA R S WEA/70)? H05/m0 .x M100/f5 7 t .w f v .wm .0% 0n M E u .7, f/. w f F- 0 l 555 N M nq mm.

3,074,472 FUEL FEEDNG SYSTEM FR GAS ENGNES This application is a continuation of my copending application Serial No. 468,233, filed February' 4, i954, now abandoned, which is a continuation oi my now aba,.- doned application Serial No. 42,302, tiled August 3, i948.

When gas turbine engines are used in vehicles such as aircraft, the pilot or operator should be able to accelerate and decelerate to selected speeds or loads by manipulating a -suitable power control device without producing dangerously high `temperatures in the burner system, stalling the compressor or dieout due to burner failure. ln order to have maximum power available for acceleration, it is desirable to supply as much `#fuel as the burners will consume without overheating, but in engines having certain characteristics, temperature is not the only limitation which must be observed, since the compressor will tend to lsurge and even stall at certain engine speeds unless a predetermined ratio of fuel to air is maintained. For engines having certain characteristics, the surge and/ or stall region may lie in the areas indicated in FGURES 3, 4, 6 and 7 where fuel flow is plotted against engine rpm. Once this region is known, it can be avoided by properly controlling the irate of fuel feed, and an object of the present invention is to provide means whereby such control is obtained automaticly while at the same time permitting acceleration at the will of a pilot or operator.

Another object is to better adapt a fuel feed and power control device such as is disclosed in the copending applications of Frank C. Mock, Serial Nos. 596,62l and 716,154, tiled May 30, 1945, and December i3, 19%, and now Patent Nos. 2,58l,276 and 2,689,606, respectively, common assignee to gas turbine engines having certain chmacteristics.

A further object is to provide a fuel feed system for gas turbine engines wherein the rate of fuel feed to the burners may be varied automatically along an acceleration and/ or a deceleration curve 4to obtain maximum efticiency or power output in the high power range oi operation and to avoid burner failure or dieout upon throttling back to the idle or low power range of ope-ration.

Another object of this invention is to provide a method of accelerating engines of the type speciiied without encountering compressor instability.

The foregoing and other objects and advantages will become apparent in view of the following description taken' in conjunction with the drawings, wherein:

FlGURE l is a view in side elevation and partly broken away of a gas turbine propeller equipped with a fuel control system iu accordance with the invention;

FIGURE 2 is a sectional schematic view of the fuel control system;

FIGURES 3 and 4 are curve charts illustrating the operation of the fuel control system of FEGURE 2;

FEGURE 5 shows a somewhat modied version' of the control system shown in FIGURE 2; and

FGURES 6 and 7 are curve charts illustrating the operation of the control of FlGURE 5.

Referring lirst to FIGURE l, the engine in general comprises a compressor y1G (shown as of the axial ilow type) which forces air into an annular header ll arranged to direct it to a plurality of annularly spaced combustion chambers l2 each containing a burner or generator tube E13 having air inlet holes in the walls thereof through which at least part of the air is ed for admixture with fuel to produce combustion. The burners discharge into a collector ring ld arranged to direct the hot air and products of combustion through a set of stationary distributing blades l5' against the Vblades lo of a turbine rotor i6. rlhe turbine lo drives the air compressor and these components may be mounted on a common shaft, not shown, or may be drivingly coupled through transmission mechanism. The turbine, in ado non to driving the compressor, is adapted to drive a propeller Il provided with propeller blades 17, which may be of the variable pitch type well known in the market and provided with suitable pitch changing mechanism i8 including a control lever i9 having connected thereto a link 2@ which is shown extending back to a coordinating box 2l housing suitable mechanism `for coordinating the various engine controls under a single lever 22, the latter onnecting by means oi a link 23 with a pilots power control lever The coordinated mechanism forms no part of the present invention; it is simply shown as illustrative of accessory equipment for engines of this type. The coinpressor lo is mounted in a casing or housing 25, ard forwardly of this casing is a flared air intalie or cov/ling 25 which opens in the direction of aircraft travel. The part indicated at 2'7 houses reduction gearing between the tiubine and propeller drive. As will be understood, part of the energy (usually the major part) resulting from th combustion expansion of the precompressed air and `fuel is utilized in driving the propeller, while the reuainder is utilized as jet thrust in a reaction tube housed in a tail piece 26.

The present invention is primarily concerned with the fuel supply device or system shown schematically in FlG* Rl 2, the principal parts of the system being disposed in a housing generally indicated at 3l? in PlGURE l, where the unit is located adjacent the coordinating box and is provided with a control lever which connects with said box by way o link 32. ln this manner, both the rate of fuel feed and propeller pitch may be controlled through a single lever 2d. Gbviously the lever 3l could be controlled independently of propeller pitch or it could serve as the sole power control, as desired, or found expedient.

The device in the main comprises a regulator section or body, generally indicated at 33, which is divided into chambers 3d and 355 by a diaphragm 35. A regulator valve 37 is connected to the diaphragm 3e by means of a stem Citi having a grooved member secured thereon for a purpose to be described. A spring is mounted in chamber 35' and at its inner end bears against the diaphragm 36; it constitutes a minimum metering head regulator in that it determines the mini rum value of the metering head at engine speeds which may be so low as to otherwise result in instability of the regulator.

Fuel is supplied under pressure to the regulator by way of a conduit 4l, 4l having mounted therein suitable fuel pressurizing means such as an engine driven iuel pump d2, the conduit 4l terminating in an annular valve chamber d3. The supply (Pl) pressure is maintained at a predetermined value over and above metered -ruel (P4) pressure by means of a by-pass valve AES which controls the return flow of fuel trom conduit l by way of conduit 46 and valve chamber e7 to annular chamber le and conduit i9 back to conduit el, or baci; to the low pressure or input side of pump Valve has its stern connected to a diaphragm 5d having on one side thereof a chamber Si which is vented to supply pressure by conduit 52 and on its opposite side a chamber 5.3 which is vented maeva to metered fuel (Pri) pressure by way of passages 54 and 55. rhe fuel supply (P1) pressure will therefore be maintained at a constant value above metered fuel or nozzle discharge (P4) pressure as determined by the strength of spring 56.

A safety or maximum pressure relief valve is indicated at 5S; it is designed to prevent dangerous pressures in the system due, for example, to the ow of fuel to the burners being suddenly cut off while the engine is running.

A control section or body is generally indicated at 60; it contains a speed metering head generator 61 carrying centrifugal weights 61 and an engine speed governor 62 carrying centrifugal weights 62', both said'head generator and said governor in the example illustrated being carried by a common shaft 63 provided on its outer end with a pinion gear 64 adapted to be driven from the engine.

The speed metering weights 61' are operatively connected to the regulator valve 37 by means of a slide bear` ing 65 having flanged ends 65' and 65, and a lever 66 pivoted or fulcrumed at 67, said lever at its lower end i engaging the member 39 on valve stem 38. When the shaft 63 is rotated, the governor weights 61', acting through the lever 66 and yoke 39, exert a force proportional to the lsquare of engine speed in a direction tending to open the valve 37.

A fuel feed or metering restriction is indicated at 69; its area is controlled by a fuel feed or throttling governor valve 70 which is provided with a stem 71 carrying a thrust bearing 72 at its inner end, the outer race 72 of which is engaged by the inner ends of the pivoted governor weights 62. A governor spring 73 encircles the Valve stem or rod '71 and at its inner end abuts a thrust bearing or plate 74 carried by the said rod and at its outer end receives a contact plate 75. A lever 76 is secured on a shaft '77 rotatably mounted in the casing or frame of the unit and having secured on its outer end the throttle or control lever 31. When the levers 31 and '76 are rotated in a counterclockwise direction, the governor spring 73 is compressed, the valve 70 is opened and simultaneously the governor Weights 62 are set inwardly; a clockwise movement of said levers has the opposite effect. The pilot selects any desired engine speed by varying the degree of compression of governor spring 73; the spring force which tends to open the governor valve, is opposed by the governor weight force which tends to close the valve. These two opposing forces cause the governor valve to seek a position of equilibrium at any given selected engine speed, at which the fuel ow to the engine burners maintains engine speed at the selected value as the force output of said weights equals the force output of said spring. During an acceleration of the engine to a new selected speed, for example, the unbalance between the opposing forces acting on valve 70 causes said valve to remain in a fixed wide open position until the increasing force output of the governor weights begins to overcome spring 73 at or near selected speed, and the valve moves towards closed position to cut-off fuel flow and govern the engine to selected speed.

The chamber 34 communicates by way of a passage 7S with governor chamber 79, and the latter communicates with chamber 80 in which the valve 70 is mounted. When the valve 70 is opened, fuel is metered across the valve into annular chamber 81 and thence Hows by way of passage 82 to the metered fuel line 82, see FIGURE l, and manifold ring 33. From this manifold ring, individual fuel lines $4 feed the fuel to the respective discharge nozzles S5 of the burners or generators 13. These nozzles may be of any suitable type adapted to open under pressure and spray fuel into the combustion chambers.

A fuel cut-off valve 86 is usually mounted in the conduit 82 to fully cut off flow of fuel to the engine when the latter is shut down.

Since a gas turbine tends to consume less fuel for a given throttle setting as the density of the air decreases with changes Vin altitude, it is desirable to provide for Li density compensation. This is accomplished by a density circuit including a control bleed 90 between the chambers 34 and 35, passage 91, chamber 92, valve chamber 93 and passage 94 terminating in the metered fuel conduit 82. A valve orifice 95 is delined between chambers 92 and 93 and is controlled by a contoured needle valve 96 provided with a stem 96' connected to a slide rod 97 which in turn is connected to the movable end of an aneroid or bellows 98, preferably loaded for response to changes in both pressure and temperature (see Patent No. 2,376,711 to FrankV C. Mock) and located where it will be subject to compressor inlet pressure. The manner in which this density circuit operates will be more fully set forth in the description of operation.

For a more complete illustration and description of the device so far described and shown schematically in FIG- URE 2, reference may be had to the copending application of Frank C. Mock, Serial No. 716,154, now Patent No. 2,689,606.

In order to carry out the objects ofthe invention, a contoured needle valve 100 is provided and is connected to a diaphragm 101 having chambers 102 and 103 on opposite sides thereof which are respectively in communication with the chambers 34 and 35 (P2 and P3 pressures) by means of passages 104 and 105. The diaphragm 101 is backed by a spring 106 which is adjustable by means of a screw 107 engaging at its inner end an anchor 10S on which the spring is seated. The needle 100 controls a port 109 which separates supply pressure conduit 110 from annular valve chamber 111. Fuel from chamber 111 flows by way Vof passage 112 to the passage 55 and thence tothe metered fuel conduit 82.

Operalon Usually an electric starting motor is used to crank the engine while at the same time fuel is fed to the burners and ignited, and cranking continued until the engine attains a self-sustaining speed. In tracing the ow of fuel through the metering system, it may be assumed that the latter is empty at ground level, in which event the differential across the diaphragm 36 would be substantially zero and the regulator valve 37 would -be open under the influence of the idle spring 40. If the throttle valve 70 is at idle or some partly open position and the engine is cranked, fuel will ow through the conduit 41, 41', and across the regulator valve 37 to chamber 34, from which it flows through passage 78 and chamber 79 across the valve 70 and then through conduit or passage 82 and fuel line 82 to the manifold ring 83 (FIGURE 1), and thence to the discharge nozzles by way of the individual fuel lines 84. A limited quantity of fuel will also flow through the control jet 90 to chamber 35 of the regulator and thence through the passage 91, orice 95 and passage 94 to the conduit or passage 82.

The spring 40 has little effect on the differential across the diaphragm 36 at fuel Hows above idle; its purpose is primarily to predetermine the minimum value of metering head across the governor valve 70 at speeds which may be so low as to result in instability of the control. rl`he pressure differential across the diaphragm 36 (PZ-P3) is proportional to that which is imposed across the governor or throttle valve 70 (P2-P4), and since both of these differential are substantially proportional to the square of engine speed, for any given position of the governor Ivalve 70 and the density needle 96, the velocity and hence the rate fuel ow acrossV the value 70 will be proportional to the square root of this differential, or to the speed directly. Actuation of the governor valve 70 by the levers 31 and '76 and spring 73 in a direction to increase the area of the metering opening 69, and thereby fuel feed and engine speed, causes a momentary decrease in the Vpressure drop across the Valve 70 and a consequent decrease in the differential across the diaphragm 36, whereupon the force exerted by the speed metering weights 61 causes the regulator valve 37 to move towards open position and increase the pressure drop PZ-PS until the resulting force imposed on the diaphragm 35 again equals the effective force output of weight d; the metering head (P2-4i) increases with PZ-PS to cause an increase in the iiow of fuel to the burners and in engine speed. Movement of levers 3l and 76 in a clockwise or decelerating direction extends spring 73 and allows the governor valve 70 to move towards closed position; a momentary increase in the drop across the valve 7? and a consequent increase in the dilferential across the diaphragm 36 results. This increase in P2P3 causes the regulator valve 37 to move towards closed position until the force across diaphragm 36 again balences the force output of weights el at the existing speed; a sharp decrease in fuel feed to the engine results and the engine decelerates until the governor weight force output equals the reduced governor spring force, at which time the governor valve iti attains a condition of equilibrium at the reduced speed setting.

During acceleration and deceleration, the metering head P12-Fd, and hence the rate of fuel feed, will increase and decrease as a function of engine speed along with the differential P2-P3 across diaphragm 36. The quantity of air delivered to the burners will, of course, also vary as a function of engine speed.

Upon a decrease in the density of the air flowing to the engine, less fuel is required to drive the turbine and compressor at -a given speed, and unless the maximum rate of fuel delivered to the engine on acceleration is correspondingly reduced, much higher burner temperatures will be experienced during acceleration at altitude than would he the cas-e at sea level under similar engine conditions, due to the extremely rich fuel-air ratio. It can he assumed for an engine of the type herein described that the rate of fuel feed required to maintain a given speed varies approximately directly with the entering air density. lf a pilot or operator were to carefully nurse the power control lever during acceleration and adjust the governor valve 7u in a manner such that the rate of fuel feed increased in direct relation to engine speed, compensation for changes in density by regulating the differential across the governor valve would not be necessary, but the control would then be so sensitive as to be impractical; and this also holds true during deceleration. Again, in gas turbine engines for aircraft, it may be desirable to have a relatively high idling speed to insure against engine failure when in the air, and this correspondingly reduces the range of governor valve movement and increases sensitivity between low and high power settings.

The density control circuit operates in the following manner: Decrease in entering air density causes elongation of the bellows and an increase in the area of the orilice 95, while an increase in air density has the opposite effec For a given engine or turbine speed, the differential across the metering head regulator diaphragm 36 will be constant, and hence the flow through the control jet 90 will remain constant. All ilow of fuel through the jet 91"? will pass through the orifice 95, and hence the drop across the latter will vary inversely as the square of its area; and for a fixed or given position of the needle 9d (constant density) the drop across the orifice 95 will be proportional to the drop across the control jet 9G. The sum of the rop across the orice 95 and the drop across the diaphragm 36 (or jet 9d) is equal to the drop across the governor valve 79, and at a given density, the total drop will `be proportional to the square of engine speed. lf the etective area of the orifice d is enlarged, there will be a corresponding decrease in the drop across this orice. This will lower the P3 pressure and momentarily increase the l-t 3 dierential across the diaphragm 36, whereupon the regulator valve will move toward closed position and reduce the metering head; a decrease in the er ective area of 95 having the opposite effect. Thus, if the governor 7d is opened for acceleration at altitude, less el will be supplied to the burners than would be the case for a similar position of said valve at ground level or some lower altitude. By suitably contouring the density needle h6, substantially complete density compensation may be obtained. This advantage is not only present during acceleration and deceleration, but the density circuit will also maintain a given engine or turbine speed at all altitudes for any given or iixed position of the power control lever 24 (or the throttle lever 3i).

Coming now to the operation of the circuit for circu'nventing stall, it will be noted that the diaphragm is in parallel with the regulator diaphragm 36, and hence this diaphragm itil will also be positioned as a function of engine speed; and the spring lila may be adjusted so that the differential will become effective on the needle le@ at selected engine speeds. The needle lili) which is connected to the diaphragm lili, controls the area of orilice le@ which connects the fuel in conduit il@ at pressure Pl with the fuel in conduit lf2 at pressure P4. Since lay-pass valve 45 functions to maintain the Pl--Pli pressure drop constant at all times, orifice N9 liows a constant quantity of fuel for any given position of needle illu regardless of changes in altitude. When the engine speed attains a value such that the differential across the diaphragm idd will cause needle fitti to open the orifice 109, there will be a flow of fuel across said orifice, and thence by way of passages lf2- and 5d to the metered fuel passage 32. This ilow of fuel is additive to that metered across the governor valve '7u and it will cut in and out automatically.

if inemciencies of a gas turbine engine for aircraft are disregarded, in general it may be sa`d that air iiow varies substantially linearly with engine speed; and to maintain a constant temperature at the turbine inlet, fuel flow should also vary substantially lin-early with engine speed. in actual practice, it has been found that an engine utilizing a centrifugal compressor will adhere more closely to linear air and fuel iiow characteristics than an engine utilizing an axial compressor.

Referring now to FGURES 3 and 4, the curve M5 represents the fuel feed required for steady speed at a given propeller pitch. The dot and dash line M6 represents the maximum delivery of the fuel pump d2. Let it be assumed that the engine is operating at point lll' and the pilot opens the governor valve itl -suiiiciently to accelerate to point lf3; then the fuel supplied during this period of acceleration will follow the arrows from ll7 to il@ on the l300 F. temperature line i211 and will continue in substantially linear relation to engine speed to point lit). The initial increase in flow represented by the vertical arrows occurs as a result of the increase in the effective area of the governor valve at the then existing speed. At point 12d the needle lit? becomes edective and the line ZZ is added to lll, producing an increase in burner temperature to say l50 r. at litt, which can be assumed to still be below the stall region at the existing engine speed for the particular type of engine being considered while at che vsame time giving good acceleration. In FlGUiE 4 the curves correspond to those of FIGURE 3 except in this instance the engine is operating `at some hivh altitude, say 35,600; and the Lnel feed required for the same speed as in FIGURE 3 is much less. Here an uncompensated addition for acceleration (line 22) may prove of advantage for certain types of engines due to the fact that surge is `aiiected `by temperature and the tendency to surge increases with a decrease in atmospheric temperature, and to maintain a given speed or power output, the rate of fuel feed should he increased as the entering air temperature drops. Thus, in FlGURE 4, the percentage addition represented by the uncompensated line 122 is greater at altitude than at sea or ground level since the compensated fuel represented by curve lil is much less. For example, the curve 121 could be compensated to give 1389" F. at high altitude and lll-50 l?. at ground level, and in each instance the increase in temperature resulting from the addition of curve 22 could net l500 F. for the upper limit of acceleration. Obviously, the needle 1li@ may be contoured to give diderent congurations to curve 122.

The advantages of automatic enrichment are not confined to avoidance of the stall region, since enrichment at some predetermined point on the acceleration curve may improve eliiciency and result in a higher power output for a given throttle setting. Thus, for example, an engine may have an efficiency characteristic such that to maintain a constant temperature within a given limit during acceleration it will be necessary to feed fuel at a substantially linear rate with respect to engine speed until a certain speed is attained, and then increase fuel feed above the linear rate.

Also, enrichment when throttling back to the idle range may avoid -dieout or burner failure. ln FIGURE 3, the idle curve or line is indicated at 12d. lf it be assumed that the pilot or operator wishes to decelerate from point 118 to point 125 and moves the throttle lever back to idle position, the flow of fuel will folloul the anrows between these two points. The iirst action is the closing of the throttle valve to idle position, which sharply reduces fuel flow but since the engine is still running at a relatively high rate of speed, the valve remains open. lt starts to close at 126, just above the dieout region, and when it is fully closed, the engine is operating only on idling fuel.

The idle curve is not shown on FIGURE 4. FIG- URE 5 illustrates how the fuel metering device of FIGURE 2 may be modified to produce density compensation for the added acceleration fuel. ln this figure, parts which correspond to those of FIGURE 2 are given similar reference numerals. The difference lies in the enrichment acceleration fuel circuit at the lower rightha-nd portion of FIGURE 5. The needle 130 (which corresponds to the needle 169 of FIGURE 2) controls variable orifice 131 and is connected to a diaphragm 132 having chambers 133 and 134 on opposite sides thereof, the chamber 133 being vented to the regulator chamber 34 by passage 135 and the chamber 134 'being vented to the chamber 35 of said regulator by passage 136. The diaphragm 132 is backed by a spring 137 which is anchored to a block or abutment 13S adjustable by means of a screw 139. rThe orifice 131 controls communication between chamber 133 and a passage 14d, which communicates with the passage 55 leading to the metered fuel conduit or passage 32. The maximum open position of needle 130 is adiustably determined by a contact member 141 adapted to engage an adjustable stop 142'.

FlGURES 6 and 7 illustrate the operation of the fuel metering device of FIGURE 5. In this instance, the curves which correspond to those of FiGURES 3 and 4 are given similar reference characters except that a prime has been added. These figures also illustrate a condition wherein surge limit requires a dip in fuel ow in the medium speed range. It will be seen that the flow of fuel from chamber 34 by way of passage 135 andthe chamber .133 and across the orifice 131 is compensated for changes in density in the same manner as compensation i's obtained for the pressure drop `across governor valve 70. ln other words, as altitude is gained, the bellows 9S eX- pands, enlarging the area of the orifice 95 and reducing the head across the governor valve 70, 'while at the same time reducing the head across the needle 130, so that the added acceleration fuel varies with changes in density. The contour of the needle 13u determines the arrow line between points 120 and 123. At 123 the valve 130 would no longer open due to the contact member 141 engaging the stop 142. Then assuming a constant governor valve area and a constant area for valve 13), metering would continue from 123 to 113 at maximum speed. Upon deceleration, the action as illustrated in FIGURE 6 is substantially the same a's in FlGURE 3 except that there is compensation for changesrin altitude.

in FlGURE 5 the percentage effect of the needle 130 is the same at sea or ground level as at altitude. This type of control may be more suitable for engines having certain characteristics, The contour of needle 133 and adjustment of spring y1337 determine the effect of the needle on the overall flow represented by the curve 122.

Although only two embodiments of the invention have been illustrated schematically and described, certain changes in form and relative arrangement of parts may be made as dictated by requirements and practical use.

I claim:

l. 1n a fuel feed and power control system fora gas turbine engine having a burner or generator to which air is supplied under pressure by a dynamic compressor driven by the turbine, means defining a fuel conduit having a fuel feed or metering restriction therein, a throttle valve for varying the area of said restriction to accelerate and decelerate the engine, pressure regulator means for automatically controlling a metering head across said restrio tion including a regulator valve, pressure responsive means connected to said regulator valve and means for producing a differential across said pressure responsive means as a function of engine speed to maintain the metering head across the throttle Valve within predetermined upper limits during acceleration, means responsive to changes in density of the air llowing to the engine for also varying the metering head, a fuel pump for pressurizing the fuel flowing to the regulator valve, means defining a flow passage arranged to by-pass pressurized fuel from a point upstream of said regulator valve around said throttle valve, a contoured valve controlling ilow of fuel through said by-pass, and means responsive to the differential across said first named pressure responsive means for controlling said latter valve.

2. lu a fuel feed .and power control system for a gas turbine engine having a burner or generator to which air is supplied under pressure by a dynamic compressor driven by the turbine, means defining a fuel ow conduit for conducting fuel to the burner having a fuel feed or metering restriction therein, a throttle valve for varying the 'area of said restriction to accelerate .and decelerate the engine, pressure regulator means for controlling a metering head across said restriction including a regulator valve,

ing with variations in engine speed to maintain the metering head across the throttle valve within predetermined upper limits during acceleration, a fuel pump for pressnrizing fuel flowing -to said regulator valve, a return circuit for the pressurized fuel having a relief valve operatively associated therewith, means responsive to changes in density of the air flowing to the engine arranged to also vary the metering head across said throttle valve, means defining a flow passage for conducting added acceleration fuel from a point upstream of said regulator valve to said conduit beyond said throttle valve, said latter flow passage communicating with said relief circuit through a variable ow orifice, a valve controlling said latter orifice,Y a diaphragm connected to said latter valve, and means for subjecting said latter diaphragm t0 the differential across said first named diaphragm t0 thereby initiate a ow of additional acceleration fuel t0 that metered across the throttle valve when the engine speed attains a predetermined valve.

3. ln a fuel feed and power control system for a gas turbine engine having a burner and a compresso-r, a fuel conduit for conducting fuel to the burner having a -restriction therein, first means responsive to changes in engine speed arrangedY for controlling the area of said restriction, speed signal generating means responsive to changes in engine speed and operatively connected to said first means in such a manner that the fuel pressure differential across said restriction is controlled to vary as a function of engine speed, and a third means responsive to the speed signal generated by said generating means for l causing, at a predetermined engine speed during an acceleration of the engine, a liow to the burner in addition to the flow regulated by the restriction.

4. In a fuel feed and power control system for a gas turbine engine having a compressor for supplying air under pressure to a burner in which a combustible mixture of air and fuel is burned, a fuel conduit for conducting fuel to the burner, first engine speed responsive means arranged for controlling the iiow of fuel to the burner during steady state operation of the engine, mechanism for controlling said first means to initiate acceleration of the engine by causing an abrupt enrichment of the fuel owing to the burner and .a first resultant increase in the ratio of fuel-to-air burned therein, second engine speed responsive means for establishing a predetermined rate of change of fuel liow to the burner during acceleration of the engine below a predetermined speed, and third means operative as a function of engine speed for causing, during acceleration of the engine above said predetermined speed, an additional enrichment of the fuel flowing to the burner and a second resultant increase in the ratio of fuelto-air burned therein.

5. In a fuel feed and power control system for a gas turbine engine having a compressor for supplying air under pressure to a burner in which a combustible mixture of air and fuel is burned, a fuel conduit for conducting fuel to the burner, first means including a rst variable restriction arranged for controlling the flow of fuel to the burner during steady state operation of the engine, mechanism for controlling said first means to initiate acceleration of the engine by causing an abrupt enrichment of the fuel flowing to the burner and a first resultant increase in the ratio of fuel-to-air burned therein, second means including a second variable restriction in series with said first variable restriction operatively connected to said first means for establishing a rate of change of fuel flow to the burner which results in a decrease in the ratio of fuel-to-air burned therein during an acceleration of the engine below a predetermined speed, and third means `operative during acceleration of the engine above said predetermined speed for causing a ow to the burner in addition to the ow regulated by said variable restriction.

6. In a fuel feed and power control system for a gas turbine engine having a compressor for supplying air under pressure to a burner in which a combustible mixture of air and fuel is burned, a fuel conduit for conducting fuel to the burner, first means including a first variable area restriction arranged for controlling the ow of fuel to the burner during steady state oper-ation of the engine, mechanism for controlling said first means to initiate acceleration of the engine by causing an abrupt enrichment of the fuel owing to the burner and a first resultant increase in the ratio of fuel-to-air burned therein, second means including a second variable area restriction in series with said rst variable area restriction operatively connected to said first means for establishing a predetermined rate of change of fuel flow to the burner during It) acceleration of the engine below a predetermined speed, and third means including a third variable area restriction in parallel with said second variable area restriction operative [during acceleration of the engine above said predetermined speed for causing liow to the burner in addition to the flow regulated by said rst means.

7. In a fuel feed and power control system for a gas turbine engine having a burner and a compressor, a fuel conduit for conducting fuel to the burner having a first and second restrictions in series iiow relationship and a third restriction in parallel flow relationship with said first and second restrictions, first means including a first valve member responsive to changes in engine speed arranged for controlling the area of said first restriction, second means including a second valve member responsive to changes in engine speed operatively connected to said first means for controlling the area of said second restriction such that the fuel pressure differential across said first restriction is controlled to vary as a function of engine speed, and a third means including a third valve member responsive to a change in engine speed for controlling the area of said third restriction, said third means being operative, at predetermined engine speed, to cause flow Ito the burner in addition to the viiow regulated by said restriction.

8. ln a fuel feed and power control system for a gas turbine engine, a fuel supply conduit having a rst restriction therein, a lirst valve for controlling the effective area of said restriction, adjustable engine governing means operatively associated with said rst valve, other means including a second restriction and second valve member for controlling the eifective area thereof in series with said first restriction for automatically maintaining the rate of fuel feed within predetermined limits during a transition in engine speed following adjustment of said governor and for generating a signal which varies as a function of an engine operating condition, and fuel regulating means operatively connected to said other means and responsive to 4the signal generated thereby, said fuel regulating means including a third restriction and third valve member for controlling the effective area thereof in parallel with said second restriction and being operative at a predetermined value of said engine operating condition to produce a ow to the burner in addition to the ow through said restriction, said third valve member being operative to cause a progressive increase in the effective iiow area of said third restriction and thus fuel ow through said yconduit as la function of said engine operat- Iing condition at values in excess of said predetermined value to effect a corresponding increase in turbine inlet temperature.

References Cited in the le of this patent UNITED STATES PATENTS 2,117,105 Schimanek May 10, 1938 2,414,322 Mock Ian. 14, 1947 2,581,275 Mock Jan. 1, 1952 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,074,472

It s hereby certified that error appears in the ent requiring correction and that the said Letters Pat corrected below.

Column 3, line 63, after "ennuis-sr" E31 a coumiline 63, 01 "dieenie" Ewa; 5 celumz 5, line Y, after gfeve^ne" insert VE I f :s 7 o, me ed, "ve-Ive" Teac! velue sriae "rf".

Signed enc? sealed 'this day el" Lie.,

SEAL) tterst:

ERNEST W. SWIDER DAVID L' LADD Attesting Officer Commissioner of Patents 

1. IN A FUEL FEED AND POWER CONTROL SYSTEM FOR A GAS TURBINE ENGINE HAVING A BURNER OR GENERATOR TO WHICH AIR IS SUPPLIED UNDER PRESSURE BY A DYNAMIC COMPRESSOR DRIVEN BY THE TURBINE, MEANS DEFINING A FUEL CONDUIT HAVING A FUEL FEED OR METERING RESTRICTION THEREIN, A THROTTLE VALVE FOR VARYING THE AREA OF SAID RESTRICTION TO ACCELERATE AND DECELERATE THE ENGINE, PRESSURE REGULATOR MEANS FOR AUTOMATICALLY CONTROLLING A METERING HEAD ACROSS SAID RESTRICTION INCLUDING A REGULATOR VALVE, PRESSURE RESPONSIVE MEANS CONNECTED TO SAID REGULATOR VALVE AND MEANS FOR PRODUCING A DIFFERENTIAL ACROSS SAID PRESSURE RESPONSIVE MEANS CONNECTED TO SAID REGULATOR VALVE AND MEANS FOR PRODUCING A DIFFERENTIAL ACROSS SAID PRESSURE RESPONSIVE MEANS AS A FUNCTION OF ENGINE SPEED TO MAINTAIN THE METERING HEAD ACROSS THE THROTTLE VALVE WITHIN PREDETERMINED UPPER LIMITS DURING ACCELERATION, MEANS RESPONSIVE TO CHANGES IN DENSITY OF THE AIR FLOWING TO THE ENGINE FOR ALSO VARYING THE METERING HEAD, A FUEL PUMP FOR PRESSURIZING THE FUEL FLOWING TO THE REGULATOR VALVE, MEANS DEFINING A FLOW PASSAGE ARRANGED TO BY-PASS PRESSURIZED FUEL FROM A POINT UPSTREAM OF SAID REGULATOR VALVE AROUND SAID 